JP2001276867A - Anaerobic and aerobic activated sludge treating method and equipment therefor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an anaerobic and aerobic activated sludge treating method which is capable of stably maintaining the good removal of a BOD component and nutrient salt component for a long period. SOLUTION: The device is provided with a second activated sludge treating vessel 3 in communication with a first activated sludge treating vessel 2 into which a water to be treated flows continuously. The respective treating vessels are provided with aerators 14 and 24 for putting the inside of the treating vessels into an aerobic or anaerobic state by the aeration quantity or aeration stoppage meeting an input control signal. The respective treating vessels are provided with pH meters 11 and 21, DO meters 12 and 22 and ORP meters 13 and 23 and pH maximal point detecting means 17 and 27 with noise removal filters are connected to the respective pH meters. A calculating means 28 for a DO decreasing rate in the anaerobic state is connected to the DO meter of the second treating vessel. The fuzzy control rule 33 having each of the anaerobic and aerobic states of the respective treating vessels, the time for detection of the pH, DO, ORP and pH maximal point and the DO decreasing rate of the second treating vessel 3 as a precondition part variable and the aeration quantity of the aerators 15 and 25 as a post condition part variable is stored into a controller 30. The switching of the anaerobic and aerobic states of the respective treating vessels and the adequate aeration quantity are controlled in accordance with the control rule 33.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method and an apparatus for treating anaerobic / aerobic activated sludge, and in particular, alternately performs aeration treatment and non-aeration treatment (treatment in which the inside of a treatment tank becomes anoxic and anaerobic by stopping aeration). The present invention relates to an activated sludge treatment method and apparatus for removing organic matter, nitrogen and / or phosphorus in water to be treated by repeated activated sludge treatment.

[0002]

2. Description of the Related Art Conventionally, BOD in treated water such as sewage wastewater has been known.
An organic substrate (hereinafter, referred to as a BOD component) represented by (Biochemical Oxygen Demand) is mainly removed by activated sludge, which is a group of microorganisms, in an aeration tank. Recently, however, it has been required to remove nutrients such as nitrogen and phosphorus in the treated water to prevent eutrophication in closed water areas. In order to remove nitrogen and phosphorus, cost and surplus sludge generation are reduced. Many advantageous biological methods have been adopted.

As one of the biological methods for removing nutrients, anaerobic / aerobic activated sludge treatment, which is an application of the conventional standard activated sludge method, is currently receiving attention. In this method, the water to be treated is continuously flowed into one or a plurality of activated sludge treatment tanks, and aeration treatment for aeration (hereinafter, sometimes referred to as an aeration step) and aeration are stopped and only stirring is performed. Non-aeration treatment (hereinafter, sometimes referred to as a stirring process) is alternately repeated, and the treated water is sent to the final sedimentation basin, and the sludge is settled and separated. This is a method for removing phosphorus.

In the anaerobic / aerobic activated sludge treatment method, the BOD component in the water to be treated is oxidatively decomposed in an aerobic state. Ammonia nitrogen (NH ₄ -N) in the water to be treated is first nitrified by nitrifying bacteria in an aerobic state and then denitrified by denitrifying bacteria in an anoxic state. Phosphorus in the water to be treated is desorbed by first releasing phosphorus to the dephosphorus bacterium in an anaerobic state, then allowing the dephosphorus bacterium to excessively ingest phosphorus in an aerobic state, and then extracting excess sludge containing excessive phosphorus. Phosphorus.

[0005] In order to effectively remove nitrogen, aerobic sludge residence time (A-SR) is required so that nitrifying bacteria can be retained in the treatment system.
T), and the redox potential (O
xidation-Reduction Potential. Hereinafter, it is called ORP. )
During the nitrification process, the dissolved oxygen concentration (Dissolved Oxygen; hereafter referred to as DO) is 1.5 mg / l (l
Represents liter. same as below. ) It is important to keep the above and to control the pH so as not to bias the acidity because an acid is generated.

[0006] In addition, improving the phosphorus content in the sludge and reliably discharging the proliferated sludge to the outside of the system leads to an improvement in the phosphorus removal rate. Therefore, in order to effectively remove phosphorus, if sludge is retained for a long period of time, it becomes anaerobic and phosphorus may be re-released.Therefore, it is necessary to frequently extract excess sludge, and to sufficiently release phosphorus in the anaerobic process. Therefore, it is important to keep ORP as low as possible.

[0007]

However, if either nitrogen or phosphorus is to be removed alone, it is sufficient to repeat the non-aeration treatment and the aeration treatment under the above conditions. However, there is a problem that it is difficult to control non-aeration processing, aeration processing, and switching between them. This is because it is difficult to stably maintain activated sludge, which is an aggregate of microorganisms operating in different environments, for a plurality of removal targets.

For example, it is better to secure a sufficient sludge retention time (hereinafter referred to as SRT) for nitrogen removal, whereas for phosphorus removal, the SRT is shortened and excess sludge is frequently extracted. Better. That is, it is difficult to remove both nitrogen and phosphorus by the optimal setting of only SRT.

Further, it is known that in the non-aeration treatment, a denitrification reaction first proceeds, and a phosphorus release reaction proceeds after the denitrification reaction is completed. Therefore, to remove both nitrogen and phosphorus,
It is necessary to detect the completion of the denitrification reaction and switch to the aeration process before the phosphorus release starts. As one method for detecting the completion of the denitrification reaction, as shown in FIG.
Is continuously measured, and OR in non-aeration treatment (stirring process)
A method of detecting the completion of the denitrification reaction by detecting the inflection point of P has been proposed (Japanese Patent No. 2786770). However, the detection of the inflection point of the ORP is not always easy, and the detection of the inflection point may be difficult as shown in FIG. 5B, and the detection of the inflection point may be more difficult due to noise or the like. In order to ensure good nitrogen removal and phosphorus removal, it is desired to develop a method capable of reliably detecting the completion of the denitrification reaction in the non-aeration treatment.

Furthermore, activated sludge is a mixed microbial system, and changes in the environment affect the activities of living organisms in a complex manner, so that the amount of water to be treated and the quality of the water (hereinafter sometimes referred to as inflow load) fluctuate greatly. There is also a problem that it is difficult to operate the system satisfactorily and stably. Conventionally, in many cases, the fluctuation of the inflow load is dealt with by facility operation control based on empirical know-how of a skilled manager. However, it is difficult to perform optimal control for all inflow conditions and environments around the clock, and there is a need for the development of technology that can appropriately control non-aeration and aeration in response to changes in inflow load. I have.

It is an object of the present invention to provide a method for treating anaerobic / aerobic activated sludge which can stably maintain good removal of BOD components and nutrient salts for a long period of time.

[0012]

Means for Solving the Problems The present inventors have paid attention to the change over time in pH in an anaerobic / aerobic activated sludge treatment tank. In the aeration step (aeration treatment), the pH decreases due to the formation of nitrate ions by the nitrification reaction, but when switching to the stirring step (non-aeration treatment), the pH increases first due to the decrease in nitrate ions due to the denitrification reaction, and the denitrification treatment After completion, the pH drops again when the phosphorus-accumulating bacteria release phosphorus and produce phosphate ions. Therefore, it is considered that the pH maximum appears at the time of transition from the denitrification reaction to the phosphorus release reaction. However, as shown in FIG. 3 (A), the change width of the pH is very narrow and the output signal of the pH meter in the processing tank contains fine noise. Is difficult to detect.

The present inventor has studied a method of detecting the maximum of pH. As a result, the maximum of the pH can be detected by inputting the output signal of the pH meter in the processing tank through a noise removing filter. I found that. That is, as shown in FIG. 3B, if noise is cut by a filter, for example, pH
The point at which the pH changes from an increase to a decrease can be detected at the pH maximum point. In general, detection of a local maximum point is easier than detection of a bending point. The present invention has been completed based on this finding.

Referring to the embodiment shown in FIG. 1, the anaerobic / aerobic activated sludge treatment method of the present invention comprises the steps of: introducing the water to be treated 1 into an activated sludge treatment tank 2 provided with an aerator 14 and a pH meter 11; A cycle consisting of connecting the pH maximum point detecting means 17 with the noise removal filter 16 to the pH meter 11 and performing aeration processing by driving the aeration apparatus 14 and non-aeration processing from the stop of the aeration to the detection of the pH maximum point by the detecting means 17 Is repeated, and the sludge in the treated water 5 flowing out of the treatment tank 2 is settled and separated.

Preferably, a DO meter 12 is provided in the treatment tank 2, and means for calculating a DO reduction rate 28 during non-aeration processing is connected to the DO meter 12, and the driving time of the aerator 14 during aeration processing is set for each cycle. Is controlled based on the DO reduction rate during the immediately preceding non-aeration treatment. In this case, the driving time of the aeration device 14 is changed from the start of the aeration to DO.
The time until the total output exceeds the predetermined DO set value is set, and the predetermined DO set value at the time of the aeration process can be adjusted for each cycle based on the DO reduction speed at the time of the immediately preceding non-aeration process.

More preferably, as shown in FIG. 2, the first activated sludge treatment tank 2 into which the water 1 to be treated flows and the first treatment tank 2
PH meter 11, respectively with the second activated sludge treatment tank 3 communicating with
21 and aeration devices 15 and 25 are provided, and pH maximum points detecting means 17 and 27 with noise elimination filters 16 and 26 are connected to the respective pH meters 11 and 21 to perform aeration treatment by driving the aeration device in the first treatment tank 2. The cycle consisting of the non-aeration treatment from the stop of the aeration until the time sufficient for phosphorus release of the activated sludge elapses is repeated. After repeating the cycle including the non-aeration treatment up to the time of discharge, the sludge in the treated water 5 flowing out of the second treatment tank 3 is settled and separated.

[0017]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The embodiment of FIG. 1 repeats a cycle consisting of a non-aeration treatment and an aeration treatment (hereinafter sometimes referred to as an anaerobic / aerobic cycle) in a single activated sludge treatment tank 2. The following shows an example. The treatment tank 2 has an aeration device 14
, A stirrer 15 and a pH meter 11 are provided. By driving the aeration device 14 and the stirring device 15, the inside of the processing tank 2 can be in an aerated state, and by stopping the aeration device 14 and driving only the stirring device 15, the inside of the processing tank 2 can be in a non-aerated state. . The control device 10 connected to the aeration device 14
Controls drive / stop of 14.

The pH meter 11 of the processing tank 2 has a noise removing filter.
The pH maximum point detecting means 17 with 16 is connected, and the output signal of the pH meter 11 is input to the detecting means 17 via the noise removing filter 16.
As described above with reference to FIG. 3, by cutting the noise in the output signal of the pH meter 11 with the filter 16, it is possible to detect the pH maximum point in the non-aeration process. Detection means 17
Is to detect the point in time when the pH changes from increasing to decreasing based on the change in pH over time, or to detect the point in time when the rate of change in pH changes from positive to negative based on the change over time in the rate of change of pH. Is a device that detects a pH maximum point by using a computer having a built-in detection program. An example of the noise elimination filter 16 is a high-frequency noise elimination filter or a noise elimination filter based on a moving-average model described later. pH maximum point detection means 17
Is connected to the control device 10 to detect the pH maximum point
Used for control of If necessary, a pH meter may be connected to the control device 10 to use the pH of the processing tank 2 for controlling the aeration device 14.

The noise elimination filter based on the moving average model is, for example, based on the following equation (1), which converts a pH measurement value P _n ′ at a certain time n in a time series into a pH meter output signal (P _{n) at the} time _n. ) And the pH meter output signals at several points before and after the time series (for example, _Pn-4 , _Pn-3 , _Pn-2 , _{Pn- 1} , _{Pn + 1} , _{Pn + 2} ,
P _{n + 3} , P _{n + 4} )
This is to remove noise in the total output signal. For example, when taking in the pH data in the processing tank 2 every 30 seconds,
P _n-4 , P _n-3 , P _n-2, and P _n-1 are the pH meter output signals 2 minutes before time n, 1 minute 30 seconds before, 1 minute and 30 seconds before time n, P _{n + 1} , P _{n + 2} , P
_{n + 3} and P _{n + 4} indicate the pH meter output signals 30 seconds, 1 minute, 1 minute 30 seconds, and 2 minutes after time n.

In the moving average model, the parameters in the model (constant coefficients of equation (1), hereinafter referred to as weights) and the number of data to be averaged (9 in equation (1), hereinafter referred to as average score). Decisions matter. If the average score is reduced, it is difficult to remove fine noise. On the other hand, if the average points are increased, even if noise can be removed, the waveform of the actual data itself may be broken. The inventor has
When obtaining the pH measurement value P _n ′ at a certain time n, while securing a large number of average points and increasing the weight of the pH meter output signal at a time close to the time n, the noise of small fluctuations can be removed, It has been found that the characteristics of the pH waveform in the treatment tank 2 can be left.

Note that the average score and the measurement interval (for example, 30
Seconds), the parameters need not be as in the example of equation (1). Depending on the condition of the water 1 to be treated and the environment of the treatment tank 2,
The average number of points, the measurement interval, and the parameters in the moving average model can be appropriately adjusted so that the fine fluctuation noise component can be removed without canceling the characteristics of the waveform.

[0022]

(Equation 1)

The water to be treated 1 flowing into the treatment tank 2 is mixed with the returned sludge 7 and is treated by an anaerobic / aerobic cycle in a state where the sludge 7 floats, and is sent to the final sedimentation basin 4 downstream as treated water 5. Can be In the final sedimentation basin 4, the sludge in the treated water 5 is settled and separated. The treated water after sludge separation is discharged, a part of the settled sludge is returned to the treatment tank 2 as return sludge 7, and the remaining settled sludge (hereinafter referred to as excess sludge) is pulled out and disposed.

In the aeration treatment for driving the aerator 14, the BOD component in the water 1 is oxidatively decomposed and the ammonia nitrogen is nitrified into nitric acid. After driving the aeration device 14 for a predetermined time, the control device 10 stops the aeration device 14 and switches to non-aeration processing. In the non-aeration process, nitrated nitrate nitrogen is reduced to nitrogen gas and is diffused and removed to the atmosphere. During nitric acid reduction (denitrification reaction), the pH of the treatment tank 2 rises, and when phosphorus is released from sludge after completion of the reduction, the pH of the treatment tank 2 decreases. In the present invention, the pH maximum point corresponding to the completion of the denitrification reaction is detected by the detection means 17, and at the time of detection, the control device 10 restarts the aeration device 14 to switch to the aeration process.

Generally, the time of the denitrification reaction during the non-aeration treatment varies depending on the quality and quantity of the water to be treated 1, the properties of the sludge, and the like. In order to keep the removal of nutrient components in the water to be treated 1 good, it is necessary to adjust the non-aeration treatment time according to the quality of the water to be treated 1 and the like. Since the present invention switches from non-aeration processing to aeration processing in response to detection of the pH maximum point in the processing tank 2, the optimum non-aeration processing time corresponding to the denitrification reaction time is independent of the water quality and water amount of the water 1 to be treated. , And good removal of BOD components and nitrogen can be achieved.

When removing phosphorus in the water 1 to be treated, instead of repeating the anaerobic / aerobic cycle consisting of the non-aeration treatment and the aeration treatment from the stop of the aeration to the detection of the pH maximum point by the detection means 17, The cycle consisting of the non-aeration process and the aeration process by driving the aerator is repeated from the stop of the aeration to the time when a sufficient time for phosphorus release of the activated sludge has elapsed. Here, the time `` from the stop of the aeration to the lapse of time sufficient for phosphorus release of the activated sludge '' is sufficiently longer than the time `` from the stop of the aeration to the detection of the pH maximum point by the detection means 17 '', and This is a time sufficient for sufficient release of phosphorus from activated sludge after detection of the pH maximum point. Phosphorus release by activated sludge is treatment tank 2
It is considered that the reaction proceeds after the detection of the pH maximum point, so by securing sufficient time for phosphorus release after the detection of the pH maximum point, excessive intake of phosphorus by activated sludge after switching to aeration treatment is promoted, Good removal of BOD components and phosphorus in the treated water can be achieved.

Preferably, as shown in FIG. 2, a first processing tank 2 mainly for removing phosphorus and a second processing tank 3 mainly for removing nitrogen are provided in communication with each other. The phosphorus in the water to be treated 1 continuously flowing into the water 1 is removed in the first treatment tank 2, and the nitrogen in the water to be treated 1 is removed in the second treatment tank 3. A final sedimentation basin 4 is provided downstream of the second treatment tank 3. Each of the treatment tanks 2 and 3 is provided with a pH meter 11 or 21 and an aeration device 15 or 25, respectively.

In the first treatment tank 2, phosphorus is added to the activated sludge by repeating a cycle consisting of aeration treatment by driving the aeration device and non-aeration treatment from the stop of the aeration to the lapse of time sufficient to release phosphorus from the activated sludge. Excessive intake is performed to remove the BOD component and phosphorus in the water 1 to be treated. Thereafter, the water to be treated 1 is caused to flow into the second treatment tank 3. In the second treatment tank 3, the cycle consisting of the aeration treatment by driving the aeration device and the non-aeration treatment from the stop of the aeration device to the detection of the pH maximum point by the detection means 27 is repeated, so that the BOD component in the water to be treated 1 is reduced. It removes nitrogen and prevents phosphorus release reaction from sludge that occurs after detection of the pH maximum point. By sedimenting and separating the sludge in the treated water 5 flowing out of the second treatment tank 3 in the final sedimentation basin 4, good removal of the BOD component, nitrogen and phosphorus in the treated water 1 can be achieved. In the two-tank processing tanks 2 and 3 of FIG.
The effect of reducing the risk that the water to be treated 1 flows out to the final sedimentation basin 4 without being treated can be expected as compared with the single tank type treatment tank.

More preferably, the processing tank 2 of FIG.
The second treatment tank 3 is provided with a DO meter 12 or 22 for non-aeration treatment.
The DO reduction speed calculating means 28 is connected to the DO meter 12 or 22 to control the drive time of the aeration device 14 during the aeration process for each anaerobic / aerobic cycle based on the DO reduction speed during the immediately preceding non-aeration process.
In general, the DO value of the water to be treated 1 during the aeration treatment and the non-aeration treatment changes according to the amount of water and the water quality (inflow load) of the treatment water 1. When the inflow load is high, oxygen is consumed to decompose the BOD component. Therefore, even if the DO of the water to be treated 1 rises during the aeration treatment, it can be returned to the oxygen-free state in a relatively short time during the non-aeration treatment. it can. On the other hand, when the inflow load is low, it takes too much time to return to the anoxic state during the non-aeration treatment,
There is a possibility that sufficient time for the denitrification treatment cannot be secured. Therefore, it is desirable to adjust the drive time of the aeration device during the aeration process according to the inflow load.

The present inventor has noticed that the difference in the DO reduction rate during the non-aeration treatment is different depending on the difference in the inflow load. FIG. 4A shows the DO reduction speed when the inflow load is high, and FIG. 4B shows the DO reduction speed when the inflow load is low. As can be seen from the figure, the inflow load can be estimated based on the DO reduction rate during the non-aeration processing. Therefore, as shown in the illustrated example, the calculation unit 28 is connected to the control device 10 or 30, and when the DO reduction speed output by the calculation unit 28 is small, the control device 10 or 30 reduces the drive time of the aeration device in the immediately subsequent aeration process. By shortening or reducing the amount of supplied oxygen, optimal aeration control corresponding to fluctuations in the inflow load becomes possible. In addition, even in a low load state at the start of service, which is often a problem, by performing appropriate aeration control, it becomes possible to realize optimal water treatment under all inflow conditions. An example of the DO decrease speed calculating device 28 is also a computer having a built-in decrease speed calculating program.

In the illustrated example, the drive time of the aeration devices 14 and 24 is defined as the time from the start of aeration until the outputs of the DO meters 12 and 22 exceed a predetermined DO set value. When the value is exceeded, the aeration devices 14 and 24 are stopped. When the DO reduction rate in the non-aeration process calculated by the calculation unit 28 is low, the drive time of the aeration apparatus is shortened by adjusting the predetermined DO set value in the subsequent aeration process to be low. Also,
Reference numeral 29 in the figure denotes a memory provided in the DO decrease speed calculating means 28.

In this manner, the object of the present invention is to provide the "anaerobic / aerobic activated sludge treatment method capable of stably maintaining good removal of the BOD component and the nutrient component for a long period of time".

[0033]

FIG. 2 shows an example of an anaerobic / aerobic activated sludge treatment apparatus of the present invention using a fuzzy controller 30. The treatment apparatus shown in FIG. 1 includes a first activated sludge treatment tank 2 into which water to be treated continuously flows, a second activated sludge treatment tank 3 communicating with the first treatment tank 2, and a treated water in the second treatment tank 3. 5 has a sedimentation basin 4 into which it flows. The first processing tank 2 and the second processing tank 3 are provided with a first aeration device and a second aeration device, respectively, which set the inside of the processing tank to an aerated or non-aerated state by an aeration amount or an aeration stop according to an input control signal. ing.

Each of the processing tanks 2 and 3 has a pH meter.
11, 21, DO analyzers 12, 22, and ORP analyzers 13, 23 are provided. The pH meter 11 of the first processing tank 2 is connected to a pH maximum point detecting means 17 with a noise elimination filter 16, and a second processing tank is provided. A pH maximum point detecting means 27 with a noise removing filter 26 is connected to the third pH meter 21. In addition, the DO meter 21 of the second treatment tank 2 has
The DO decreasing speed calculating means 28 is connected. pH meter 11, 21,
DO total 12, 22, ORP total 13, 23, pH maximum point detecting means 17, 27,
The DO reduction rate calculating means 28 of the second processing tank 3 is connected to the control device 30.

The water to be treated 1 continuously flows into the first treatment tank 2 and is treated in the first treatment tank 2 and the second treatment tank 3 by an anaerobic / aerobic cycle to become treated water 4 and becomes the second treatment water. It flows out to the final sedimentation basin 4 downstream of the tank 3. The treated water 5 and the sludge are separated in the final sedimentation basin 4, the treated water is discharged, and a part of the sludge is returned to the first treatment tank 2 as returned sludge 7. When the BOD component, nitrogen and phosphorus in the water to be treated 1 are removed together in the two-tank treatment tanks 2 and 3, the anaerobic / aerobic cycle of each treatment tank 2 and 3 is performed for each treatment purpose. Therefore, it is difficult to control the anaerobic / aerobic cycle optimally and stably for a long period of time because it is necessary to perform the control asynchronously.

The inventor paid attention to fuzzy control. According to the fuzzy control, it is possible to systematize the empirical know-how of a skilled manager. In addition, as described above, the completion point of the denitrification reaction can be relatively easily detected from the pH maximum point at the time of the non-aeration treatment. Optimal control of the anaerobic / aerobic cycle can be expected. Furthermore, DO during non-aeration treatment
By adding the decreasing speed to the condition of the fuzzy control, it is possible to expect the optimal control of the anaerobic / aerobic cycle corresponding to the fluctuation of the inflow load of the water 1 to be treated.

The control device 30 shown in FIG. 2 performs the non-aeration / aeration treatment of each of the treatment tanks 2 and 3 and the detection of the pH, DO, ORP, and the pH maximum point.
Each of the DO reduction speeds of the processing tank 3 is determined by a variable in the antecedent part (control device 30
Of the processing tanks 2 and 3
A plurality of fuzzy control rules 33 are stored in which the aeration amount or stop of aeration is set as a consequent variable (output of the control device 30).
PH meter 11, 21, DO meter 12, 22, ORP meter 13, 2 for each treatment tank 2, 3
3. Inputting each output signal of the pH maximum point detecting means 17 and 27 and the DO reduction rate calculating means 28 of the second processing tank 3 to the control device 30;
A control signal corresponding to each output signal is output to the aeration devices 15 and 25 of each of the processing tanks 2 and 3 based on the control rule 33, and the respective processing tanks 2 and 3 are output.
Between the aeration step and the stirring step, and the optimum aeration amount in the aeration step is controlled.

The first of the anaerobic and aerobic activated sludge treatment apparatuses shown in FIG.
The transition conditions from the stirring step to the aeration step and the transition conditions from the aeration step to the stirring step in the treatment tank 2 can be arranged, for example, as shown in Table 1. In addition, the transition conditions from the agitation step to the aeration step and the transition conditions from the aeration step to the agitation step in the second processing tank 3 can be arranged as shown in Table 2, for example. Tables 3 and 4 show the control rules 33 created based on Tables 1 and 2. The control rule 33 shown in Table 3 is
The relationship between the input and output of the fuzzy control device 30 is described by the antecedent part (part of IF ~) indicating the condition and the consequent part (THEN ... part) corresponding to the output.

Table 5 shows antecedent variables of the control rule 33 in Tables 3 and 4. The antecedent variable in the present embodiment is such that each input value is -1 to 1 depending on the minimum value and the maximum value shown in parentheses.
The values standardized to the values up to are used. Also control rules
The consequent variable of 33 is the amount of aeration of the aerators 15 and 25 in each of the processing tanks 2 and 3, and the consequent variable is also normalized to a value from -1 to 1. FIGS. 6 to 10 show the membership function 32 of the fuzzy variable relating to the antecedent variable. Note that among the variables in Table 5, X02, X23, X25 to 28, X30, X31, X39, and X40 are:
Although not used in the control rules 33 of Tables 3 and 4, they can be added as antecedent variables of the control rules 33 as needed.

[0040]

[Table 1] [Conditions for shifting from the stirring process to the aeration process] (a) When DO is 0.5 mg / l or less and ORP becomes -50 mV or less for 60 minutes or more (b) DO 0.5mg / l or less and ORP is around -250mV (c) 120 minutes or more after the start of the stirring process (d) After the pH reaches the maximum value during the stirring process When more than 60 minutes have elapsed [Conditions for shifting from the aeration step to the stirring step] (e) When 10 minutes or more have elapsed since the ORP became 0 mV or more (f) 30 minutes or more have elapsed since the aeration step was started When

[0041]

[Table 2] [Transition conditions from the aeration step to the stirring step] (g) When the DO value exceeds 4.0 mg / l (h) When 60 minutes or more have passed since the aeration step (i) pH (J) When pH is 6.0 or less (k) When the decrease rate of DO in the stirring step of the previous cycle is 5.
0 mg / l · h or less and DO value exceeds 2.0 mg / l [Transition conditions from agitation to aeration process] (l) 60 minutes or more after DO value becomes 0.5 mg / l or less (M) When the ORP falls below -50 mV (n) When 75 minutes or more have passed since the start of the stirring process (o) When the pH reached a maximum value during the stirring process

[0042]

[Table 3] (a) IF X20 = NB X24> TC X00 <DA THEN Y = ON (b) IF X20 = NB X04 <OB X00 <DA THEN Y = ON (c) IF X20 = NB X16> TE THEN Y = ON (d) IF X20 = NB X38> TC THEN Y = ON (e) IF X20 = PB X22> TA THEN Y = OF (f) IF X20 = PB X16> TB THEN Y = OF

[0043]

(Table 4) (g) IF X21 = PB X09> DC THEN Y = OF (h) IF X21 = PB X17> TC THEN Y = OF (i) IF X21 = PB X17> TB X11 <HB THEN Y = OF ( j) IF X21 = PB X11 <HA THEN Y = OF (k) IF X21 = PB X09> DB X19 <RR THEN Y = OF (l) IF X21 = NB X29> TC THEN Y = ON (m) IF X21 = NB X09 <DA X13 <OA THEN Y = ON (n) IF X21 = NB X17> TD THEN Y = ON (o) IF X21 = NB X41 = PB THEN Y = ON

[0044]

Table 5 X00: DO value of the first tank (0 to 4 mg / l) X02: pH value of the first tank (5 to 7) X04: ORP value of the first tank (-300 to 0 mV) X09: Second Tank DO value (0-4 mg / l) X11: pH value of the second tank (5-7) X13: ORP value of the second tank (-300-0 mV) X16: After the process of the first tank changed Elapsed time (0-1
20 minutes) X17: Elapsed time (0 to 1) after the process of the second tank changed
20 minutes) X19: Decrease rate of DO value in the stirring step of the second tank (4 to 6 mg /
l ・ h) X20: Current process of the first tank (at 1, at aeration process-1 at
Stirring process) X21: Current process of the second tank (at 1, at aeration process-1 at
X22: Time when the ORP value is 0 mV or more in the first tank (0 to 0)
X23: Time when the ORP value is 0 mV or more in the second tank (0 to 0)
X24: Time when the ORP value is -50 mV or less in the first tank (0
X25: Time when the ORP value is -50 mV or less in the second tank (0
X26: Time when the DO value is 0.5 mg / l or more in the first tank (0
X27: Time when the DO value is 0.5 mg / l or more in the second tank (0
X28: Time when the DO value is 0.5 mg / l or less in the first tank (0
X29: Time during which the DO value is 0.5 mg / l or less in the second tank (0
X30: Elapsed time after ON / OFF switching of blower in first tank (0 to 120 minutes) X31: Elapsed time after ON / OFF switching of blower in second tank (0 to 120 minutes) X38: Elapsed time after the pH reached the maximum value in the first tank (0 to 120 minutes) X39: Elapsed time after the pH reached the maximum value in the second tank (0 to 120 minutes) X40: In the first tank Presence / absence of the maximum value of the pH during the stirring process (−1, no or 1, presence) X41: Presence or absence of the maximum value of the pH during the stirring process in the second tank (−1, no or 1, presence)

FIG. 11 is a flowchart showing the processing in the control device 30 shown in FIG. First, in step S1, the control rules 33 shown in Tables 3 and 4 and the membership function 32 shown in FIGS. Next, in step S2, each processing tank 2,
PH meter 11, 21, DO meter 12, 22, ORP meter 13, 23, pH maximum point detecting means 17, 27, and DO reduction rate calculating means 28 of the second treatment tank 3 (hereinafter collectively referred to as sensor Are output to the control device 30. Steps
In S3, the calculation means 31 of the control device 30 causes X1 shown in Table 5
Antecedent variables such as elapsed time data such as 6 and 17 are calculated based on output signals of the sensors.

In step S4, switching between aeration and non-aeration and fuzzy inference of the amount of aeration are performed based on the output signals and data obtained in steps S2 and S3, the membership function 32 and the control rule 33 read in step S1. I do. In step S5, it is determined that the control has been completed. If the control is to be continued, the process returns to step S2. For example, the above cycle is repeated every 30 seconds. The control rule 33 shown in Tables 3 and 4 is an example of performing fuzzy control in which the main purpose is dephosphorization in the first processing tank 2 and the main purpose is denitrification in the second processing tank 3.

That is, in the stirring step of the first treatment tank, it is necessary to secure an anaerobic state in order to release phosphorus from the phosphorus accumulating bacteria. The phosphorus release of phosphorus-accumulating bacteria is
It is said to be performed in the state where the ORP value is -50mV or less. Therefore, as a condition for shifting the first treatment tank from the stirring step to the aeration step, the state where the ORP value is -50 mV or less is maintained for 60 minutes (control rule a), or the stirring is performed until the ORP value becomes -250 mV. Continue the state (control rule b). Note that when 120 minutes or more have elapsed since the start of the stirring process (control rule c), or when 60 minutes have passed since the time when the pH reached the maximum value during the stirring process (control rule d), the release of phosphorus was not increased. Since it is considered that the process has already been completed, the process shifts to the aeration process.

In the aeration step of the first treatment tank, it is necessary to ensure an aerobic state in order to cause phosphorus-accumulating bacteria to overtake phosphorus. Therefore, as a condition for shifting from the aeration step to the stirring step in the first treatment tank, an aerobic condition having an ORP value of 0 mV or more can be secured for 10 minutes (control rule e). In addition,
If more than 30 minutes have passed since the aeration step, it is considered that the excessive intake of phosphorus from the phosphorus-accumulating bacteria has been completed, and if the aeration is further performed, return to the anaerobic state in the next stirring step. Immediately, the process shifts to the stirring step (control rule f).

In the aeration step of the second treatment tank, it is necessary to secure aerobic conditions in order to perform nitrification by nitrifying bacteria. Therefore, as a condition for shifting from the aeration step to the stirring step in the second treatment tank, the aeration step is continued until the DO value becomes 4.0 mg / l (control rule g). However, if the load is considered to be small, such as the DO reduction rate in the immediately preceding stirring step is 5.0 mg / lh or less, and the aeration step is continued until the DO value becomes 4.0 mg / l, Since it takes too much time to return to the anoxic state in the stirring process, the DO value is 2.0 mg / l
Then, the process proceeds to the stirring step (control rule k). In addition, when nitrification proceeds and the pH value becomes 6.0 or less (control rule j), and when the pH value becomes 6.3 or less for 30 minutes or more (control rule i), there is a possibility that the microorganisms may be adversely affected. Therefore, the process immediately proceeds to the stirring step. When 60 minutes or more have elapsed after the aeration step, the process immediately shifts to the stirring step because it is considered that nitrification of ammonia by nitrifying bacteria has already been completed (control rule h).

In the stirring step of the second treatment tank, it is necessary to ensure anoxic condition in order to perform denitrification by denitrifying bacteria. Further, in order to prevent phosphorus-accumulating bacteria from releasing phosphorus, care must be taken to prevent phosphorous release from occurring. Therefore, the condition for transition from the stirring step to the aeration step in the second processing tank is that the DO value is 0.5 mg / l or less.
0 minutes can be secured (control rule 1). Where O
When the RP value falls below -50 mV (control rule m), or when the pH takes a maximum value during the stirring process (control rule n),
Since the phosphorus release of the phosphorus accumulating bacteria starts, the process immediately shifts to the aeration step. In addition, 75
If more than one minute has elapsed, it is considered that the denitrification has already been completed, so the process shifts to the aeration step (control rule o).

In this embodiment, fuzzy inference is performed by the min-max centroid method as shown in FIG. 12 based on the above control rules 33. In this inference method, the membership function value of the fuzzy set of each condition of the antecedent part with respect to the output signal of each sensor for each control rule 33 is defined as the conformity of each control rule 33, and the minimum value (min) of the conformity of each condition Is multiplied by the membership function of the consequent part, and all control rules 33 are combined using the maximum value (max). Then, a method of using the center of gravity of the combined membership function as the output of the fuzzy controller 30 is provided. Therefore, since the inference is made comprehensively from the determination results of the plurality of control rules 33 instead of relying only on one control rule 33, it is easy to add a new control rule 33 as needed.

FIG. 12 shows an example of fuzzy inference of the first processing tank 2 based on the control rules a to f. Table 6 shows inputs of the fuzzy controller 30 in the example of FIG. The conformity of each condition of the antecedent part of the control rule a is shown in FIGS. 12A to 12C, and the minimum value (= 0.4) of the conformity of each condition of the antecedent part is multiplied by the membership function of the consequent part. The results obtained are shown in FIG. The conformity of each condition of the antecedent part of the control rule b is 0. Control rule c
The result obtained by multiplying the minimum value (= 0.4) of the degree of conformity of each condition of the antecedent part by the membership function of the consequent part is the same as that in FIG. The conformity of each condition of the antecedent part of the control rules df is 0.
It is. Accordingly, when the consequent parts of the control rules a to f are combined using the maximum value, the result is as shown in FIG. By obtaining the center of gravity shown in the figure, the output of the fuzzy controller 30 in this case is 0.74, and the fitness is 0.4. By outputting a control signal corresponding to this output to the aeration device 15 of the first processing tank 2, the aeration device 15 is driven with an appropriate amount of aeration and shifts to the aeration step.

[0053]

X20 = -1 (during the stirring process) X00 = -1 (DO value is 0 mg / l) X04 = -0.5, X22 = -1 (ORP value is -225 mV) X24 = -0.1 (ORP value However, 54 minutes after -50 mV or less) X16 = 0.8 (108 minutes after the stirring process) X38 = -1 (Maximum pH value has not been detected yet)

[0054]

As described in detail above, the anaerobic / aerobic activated sludge treatment method and apparatus according to the present invention detects the pH maximum point of the activated sludge treatment tank into which the water to be treated flows, and performs aeration by driving the aeration apparatus. After repeating the cycle consisting of the treatment and the non-aeration treatment from the stop of the aeration to the detection of the pH maximum point, the sludge in the treated water flowing out of the treatment tank is settled and separated.
It has the following remarkable effects.

(A) An optimal non-aeration treatment time according to the progress of the denitrification reaction can be ensured regardless of the quality and amount of the water to be treated, and good removal of BOD components and nitrogen can be achieved. (B) By controlling the driving time of the aeration apparatus according to the DO reduction speed at the time of the immediately preceding non-aeration processing, it becomes possible to perform optimal aeration control corresponding to the fluctuation of the inflow load. (C) In addition, even in a low load state at the start of operation, by performing appropriate aeration control, it is expected that optimum water treatment can be realized under all inflow conditions. (D) It is possible to secure the optimum growth environment of activated sludge while responding to the fluctuations in the conditions in the treatment system and the amount of inflow water, and achieve the optimal simultaneous removal of biological BOD components, nitrogen and phosphorus.
(E) By switching between the non-aeration process and the aeration process by fuzzy control, the inflow condition and environment of the water to be treated can be controlled.
It can be expected that appropriate automatic control will be performed on a time schedule. (F) By appropriately switching between the non-aeration process and the aeration process, useless operation of the aeration device can be reduced, and an effect of energy saving can be expected.

[Brief description of the drawings]

FIG. 1 is an explanatory diagram of one embodiment of the present invention.

FIG. 2 is an explanatory diagram of another embodiment of the present invention.

FIG. 3 is an example of a graph showing a pH change measured by a pH meter during a stirring process and a pH change after being processed by a noise removing filter.

FIG. 4 is an example of a graph showing the change over time of DO in the stirring step when the flowing water load is high and when the flowing water load is low.

FIG. 5 is an explanatory diagram of a conventional method for detecting an inflection point from a change over time in ORP in an aeration step and a stirring step.

FIG. 6 is an example of a membership function used in the present invention.

FIG. 7 is another example of a membership function used in the present invention.

FIG. 8 shows another example of a membership function used in the present invention.

FIG. 9 shows still another example of the membership function used in the present invention.

FIG. 10 shows another example of a membership function used in the present invention.

FIG. 11 is a flowchart of a process in a fuzzy control device used in the present invention.

FIG. 12 is an example of an inference format of fuzzy control used in the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Water to be treated 2 ... 1st activated sludge treatment tank 3 ... 2nd activated sludge treatment tank 4 ... Final sedimentation tank 5 ... Treated water 6 ... Surplus sludge 7 ... Returned sludge 8 ... Partition wall 10 ... Control device 11 ... pH meter 12 ... DO meter 13 ... ORP meter 14 ... Aerator 15 ... Agitator 16 ... Noise removal filter 17 ... pH maximum point detection means 21 ... pH meter 22 ... DO meter 23 ... ORP meter 24 ... Aerator 25 ... Agitator 26 ... Noise Removal filter 27 pH maximum point detection means 28 DO reduction rate calculation means 29 Memory 30 Fuzzy control device 31 Elapsed time calculation means 32 Membership function 33 Fuzzy control rules

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Shunsaku Yagi 5-26-15-201 Onoharahigashi, Minoh-shi, Osaka (72) Inventor Munetaka Ishikawa 20-2 Hashimoto Hashimoto, Yawata-shi, Kyoto (72) Inventor Kinoshita Shigeru 12-5 Teraguchicho, Nada-ku, Kobe-shi, Hyogo F-term (reference) 4D028 AA08 AB00 BC18 BC24 BD08 BD16 CA09 CB01 CC07 CD01 CE02 CE03 CE04 4D040 BB02 BB32 BB65 BB72 BB91

Claims (9)

[Claims] 1. An aerated apparatus and a pH meter are provided with activated water to be treated into an activated sludge treatment tank. A pH maximum point detecting means with a noise elimination filter is connected to the pH meter. An anaerobic / aerobic activated sludge treatment method comprising repeating a cycle from stoppage to non-aeration treatment from the time of detection of the pH maximum point by the detection means, and then sedimenting and separating sludge in the treated water flowing out of the treatment tank. 2. The processing method according to claim 1, wherein a DO meter is provided in the processing tank, and means for calculating a DO reduction rate at the time of the non-aeration process is connected to the DO meter. An anaerobic / aerobic activated sludge treatment method in which the driving time of the aeration device is controlled based on the DO reduction rate during the immediately preceding non-aeration treatment. 3. The processing method according to claim 2, wherein the driving time of the aeration device is a time from the start of the aeration until the DO meter output exceeds a predetermined DO set value, and the predetermined DO setting at the time of the aeration process is performed for each cycle. An anaerobic / aerobic activated sludge treatment method whose value is adjusted based on the DO reduction rate during the immediately preceding non-aeration treatment. 4. The method according to claim 1, wherein, instead of or before the repetition of the non-aeration treatment and the aeration treatment until the detection of the pH maximum point, the activated sludge is removed from the aeration stop. An anaerobic / aerobic activated sludge treatment method comprising repeating a cycle consisting of a non-aeration treatment until a time sufficient for releasing phosphorus and an aeration treatment by driving an aeration device. 5. A pH meter and an aeration device are provided in a first activated sludge treatment tank into which water to be treated flows and a second activated sludge treatment tank communicating with the first treatment tank, and noise is removed from each of the pH meters. A pH maximum point detecting means with a filter is connected, and a cycle consisting of aeration treatment by driving the aeration device in the first treatment tank and non-aeration treatment from the stop of the aeration to the lapse of time sufficient for phosphorus release of the activated sludge is repeated. In the second treatment tank, a cycle consisting of aeration treatment by driving the aeration device and non-aeration treatment from the stop of the aeration device to the detection of the pH maximum point by the detection means is repeated, and then the treatment flowing out of the second treatment tank. Anaerobic sedimentation and separation of sludge in water
Aerobic activated sludge treatment method. 6. The processing method according to claim 5, wherein a DO meter is provided in the second processing tank, and means for calculating a DO reduction rate during the non-aeration treatment is connected to the DO meter. An anaerobic / aerobic activated sludge treatment method in which the drive time of the aeration device during aeration treatment is controlled for each cycle based on the DO reduction rate during the immediately preceding non-aeration treatment. 7. The processing method according to claim 6, wherein the driving time of the aeration device of the second processing tank is a time from the start of the aeration to the time when the DO meter output exceeds a predetermined DO set value. The anaerobic condition is determined by adjusting the predetermined DO set value at the time of the aeration process based on the DO reduction speed at the time of the immediately preceding non-aeration process for each time.
Aerobic activated sludge treatment method. 8. A first activated sludge treatment tank into which water to be treated continuously flows, a second activated sludge treatment tank communicating with the first treatment tank, and a sedimentation tank into which treated water from the second treatment tank flows. A first aeration device and a second aeration device for setting each processing tank to an aerated or non-aerated state by aeration amount or aeration stop according to the input control signal, a pH meter, a DO meter, and an ORP meter provided in each of the processing tanks; P for each processing tank
PH maximum point detecting means with a noise elimination filter connected to the H meter, DO for non-aeration treatment connected to the DO meter in the second treatment tank
Reduction rate calculation means, and the state, pH and DO of each of the processing tanks
And a plurality of fuzzy control rules in which each of the ORP, the pH maximum point detection, and the DO reduction rate of the second treatment tank is set as an antecedent variable, and the aeration amount or stop of the aeration of each of the aerators is set as a consequent variable. The control device having a stored control device, each output signal of the pH meter, the DO meter, the ORP meter, the detection means and the calculation means is input to the control device, and a control signal corresponding to each of the output signals based on the control rule is provided. An anaerobic / aerobic activated sludge treatment device that outputs to each of the aeration devices. 9. The anaerobic / aerobic activated sludge treatment apparatus according to claim 8, wherein said noise elimination filter is a high-frequency noise elimination filter or a noise elimination filter based on a moving average model.